Diet Soda Can Increase Risk of Dementia and Stroke, Study Finds

Much has been written about the health risks of sugar-sweetened beverages; research has linked sugary drinks to a number of serious health risks, including obesity, heart disease, diabetes, and an early death.

Now, new research suggests diet drinks with artificial sweeteners may have some health concerns of their own.

According to a new study published Thursday in the American Heart Association’s journal Stroke, people who drank at least one artificially-sweetened beverage a day had almost three times the risk of developing stroke or dementia.

The researchers caution that the study only shows an association -- it does not prove that diet drinks actually cause stroke or dementia. Still, they say the study warrants more research in the area.

The study did not find the same link between stroke and dementia in people who drank sugar-sweetened beverages, but the authors say that does’t mean it’s time for people to start gulping those either.

“Although we did not find an association between stroke or dementia and the consumption of sugary drinks, this certainly does not mean they are a healthy option,” Matthew Pase, Ph.D., the lead author of the study and a senior fellow in the department of neurology at Boston University School of Medicine, said in a statement. “We recommend that people drink water on a regular basis instead of sugary or artificially sweetened beverages.”

The researchers analyzed data on nearly 2,900 people over the age of 45 for the stroke study and almost 1,500 people over age 60 for the dementia study.

The participants recorded their eating and drinking habits in questionnaires. The researchers reviewed this information at three different points in time over a period of seven years. They then followed up with the participants for the next 10 years to see who developed stroke or dementia and then compared dietary habits to the risk of developing these health problems.

At the end of the follow-up period, the researchers found 97 cases of stroke, 82 of which were ischemic (caused by blockage of blood vessels), and 81 cases of dementia, 63 of which were diagnosed as Alzheimer’s disease.

The researchers controlled for several other risk factors, including age, sex, caloric intake, education, diabetes, and the presence of genetic risk factors for Alzheimer’s.

The results showed that people who consumed at least one artificially-sweetened drink a day were three times as likely to develop ischemic stroke and 2.9 times as likely to develop Alzheimer’s disease dementia.

In addition to being an observational study which cannot prove cause and effect, the authors note the study several other limitations, including that the overwhelming majority of participants were white. People did not drink sugary drinks as often as diet ones, which the authors said could be one reason they did not see the same link with regular soda.

The number of people in the study was also limited.

“Even if someone is three times as likely to develop stroke or dementia, it is by no means a certain fate,” Pase said. “In our study, three percent of the people had a new stroke and five percent developed dementia, so we’re still talking about a small number of people developing either stroke or dementia.”

In an accompanying commentary, Ralph Sacco, M.D., a former president of the American Heart Association and the chairman of the department of neurology at the Miller School of Medicine at University of Miami in Florida, says that current research is “inconclusive” in determining whether or not drinking artificially sweetened beverages frequently can lead stroke, dementia, and other heart-related conditions.

However, the current study, as well as other recent research showing associations between diet soft drinks and negative effects on blood vessels throughout the body, suggest that consumers may want to use caution before turning to these drinks as an alternative to sugar-sweetened beverages.

“Both sugar and artificially sweetened soft drinks may be hard on the brain,” Sacco writes.

Other experts agree. “We know that limiting added sugars is an important strategy to support good nutrition and healthy body weights, and until we know more, people should use artificially sweetened drinks cautiously,” said Rachel K. Johnson, Ph.D., past chair of the American Heart Association’s Nutrition Committee and professor of nutrition at the University of Vermont. “They may have a role for people with diabetes and in weight loss, but we encourage people to drink water, low-fat milk or other beverages without added sweeteners.”